1. Field of the Invention
The invention relates generally to purging systems and more particularly to a purging apparatus for safe connection of harmful gas sources to process equipment.
2. Description of the Prior Art
There are numerous industrial applications which require the use of dangerous gases. Certain gases are deadly poisonous if inhaled, others are highly explosive and yet others will burn with invisible flames when they come in contact with air. Frequently, the gases are stored in steel cylinders weighing approximately 150 to 175 lbs and are stored at pressures as high as 4000 psi.
When a cylinder containing gas that is toxic, corrosive or that reacts with air is connected to process equipment all air must be flushed out or "purged" from the connecting tubing leading from the cylinder to the equipment. Also, when an empty cylinder is to be replaced, the dangerous gas must be purged from the tubing, regulator, valves, and related piping before the cylinder is disconnected. Thus, in the prior art, systems have been developed for purging the dangerous gases.
One such system is a cross-purge design which relies totally on diffusive mixing to remove the dangerous gas. The purging gas is introduced into the lines connected to the gas cylinder, allowed to mix for a short period of time, then released through a vent. This process is repeated until most of the dangerous gas is removed. However, this system has "dead-ends" where the dangerous gas may become trapped and thus not purged during the purging process.
Another purging system is disclosed in U.S. Pat. No. 4,169,486 issued to Otteman et al. Otteman discloses a small purge conduit inserted in the supply conduit so that its end terminates in close proximity to the connector to the gas cylinder. A purging is then passed through a purging conduit which then forces the dangerous gas out of the tubing near the connector to the gas cylinder. The cross-purge system has the disadvantage in that heavy gases can easily become trapped in dead-end spaces, especially near the connector to the gas cylinder. Otteman provided a means for forcing the process gas out of the space joining the connector to the gas cylinder.